The present invention relates generally to homogeneous charge compression ignition combustion engine systems and, more specifically, to a homogeneous charge compression ignition combustion engine system that can be used in a production vehicle.
Engineers and scientists in the field of combustion technology are investigating homogeneous charge compression ignition engines (HCCI engines) because they offer several benefits not currently available through other combustion engine technologies. HCCI engines are thought of as a hybrid of traditional spark ignition gasoline fueled engines and compression ignition diesel fueled engines. They have the potential to meet super, ultra-low emission vehicle standards while providing high efficiency power generation.
HCCI combustion is achieved when air, fuel and recycled exhaust gas is mixed homogeneously, compressed and auto-ignited. More specifically, combustion occurs spontaneously and homogeneously without flame propagation. In other words, there is no discernible flame front and no localized high temperature reaction region. Further, this is a lean combustion process. All of these factors contribute to a lower local flame temperature and, therefore, lower amounts of Nitric Oxide (NOx) and particulate matter in the emissions.
In the automotive arena, there are several hurdles that must be overcome prior to HCCI engines being used on production vehicles. The main obstacles include low power density, difficulty in controlling the start of combustion, high rates of heat release, and high hydrocarbon (HC) and carbon monoxide (CO) emissions. Among these, the principal challenge is control of the auto-ignition and combustion phasing.
The start of ignition is established by the auto-ignition chemistry of the air-fuel mixture, which is influenced significantly by the time-temperature history to which the mixture is exposed. It has been shown that the most effective method for combustion phasing control is to modulate the intake air temperature. Currently, an electric heater is used to regulate the intake air temperature. It is not desirable to use an electric heater on a production vehicle because the heat generated by the electric heater is either from engine output, which would decrease overall engine thermal efficiency, or from outside power, which only can be used in laboratory.
The present invention overcomes the disadvantages of prior homogeneous charge compression ignition engine systems. This system can be used in a production vehicle since it utilizes heat from existing sources to heat the air entering the engine. Specifically utilized are heat from engine coolant, heat given off by catalytic reactions and, the heat of the exhaust gas released from the engine. In fact, the heat generated from these components is usually wasted. The system disclosed here does not require an external electric heater to control the temperature of the air entering the engine.
A homogeneous charge compression ignition engine system is disclosed for controlling the temperature of the air entering the engine. The system includes a Y-junction, an intake temperature control valve, a homogeneous charge compression ignition engine, and a superintegrated heat exchanger. The superintegrated heat exchanger further includes a catalyst reaction chamber, a coolant pipe coil that is positioned adjacent the catalyst reaction chamber, and a heat exchange unit. The Y-junction and intake temperature control valve are positioned before the engine. The superintegrated heat exchanger is positioned after the engine.
Fresh air is drawn into the system through an engine throttle into the Y-junction. The Y-junction directs a potion of the fresh air into the intake temperature control valve and the rest of the fresh air to the superintegrated heat exchanger. Therefore, the Y-junction has a first outlet and a second outlet. The air that subsequently flows to the intake valve exits from the Y-junction through the first outlet and the air that subsequently flows to the superintegrated heat exchanger exits from the Y-junction through the second outlet.
The superintegrated heat exchanger is positioned downstream from or after the homogeneous charge compression ignition engine. The superintegrated heat exchanger consists of two pathways. The contents of the two pathways remain separate throughout the system.
The inlet for the first pathway is positioned for receiving the exhaust gas from the engine. First, the exhaust gas is directed through the catalyst reaction chamber. Second, the exhaust gas is directed through the heat exchange unit. The heat exchange unit is positioned adjacent to the catalyst reaction chamber. Third, the exhaust gas is directed out of the first pathway through the first pathway outlet.
The inlet for the second pathway receives fresh air that has passed through the second outlet of the Y-junction. First, the fresh air is directed around the catalyst reaction chamber and coolant pipe coil so that it is heated to a pre-heated temperature. Second, the pre-heated air is directed through the heat exchange unit to further heat the pre-heated air to a final-heated temperature. Third, the final-heated air is directed out a second pathway outlet. The second pathway outlet is connected to the intake temperature control valve. Therefore, the heated air is then fed back into the intake temperature control valve.
The intake temperature control valve has two inlets. The first inlet receives fresh air. The second inlet receives the heated air from the superintegrated heat exchanger. The intake temperature control valve has one outlet from which the mixture of fresh and heated air is directed into the homogeneous charge compression ignition engine.
In another aspect of the present invention a method of controlling the temperature of air entering a homogeneous charge compression ignition engine is disclosed. The method includes the steps of: A) heating fresh air via a superintegrated heat exchanger that extracts heat from the engine exhaust, the superintegrated heat exchanger comprising a catalyst reaction chamber and a heat exchanger unit; B) directing the heated air to an intake temperature control valve that is positioned upstream from the engine; C) mixing the heated air with unheated fresh air to obtain a mixture of heated and unheated fresh air that is at a predetermined temperature; D) directing the heated air and unheated fresh air mixture into the engine; and E) directing the exhaust from the engine through the superintegrated heat exchanger.